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LTC4015 Ready to charge but Charge suspended

Egil
on Jun 25, 2020

We have a new design, with a ESP32 controlling an LTC4015. Everything seems to be ok, it says Ready to charge, but then Charge suspended. Could someone have a look at the PCB design to see if I made some mistake? It's a KiCad design. Please tell me where to send Gerber files or what you need? Thnx in advance!

  • on Jun 26, 2020 6:48 AM 4 months ago

    Some additional details:

    There is also some problems with the I2C communication whenever VIN goes too low, below 14-15V, particularily with a good battery connected. Above or without a battery connected, communication is mostly good with occasional dropouts.

    The circuit is powered by a benchtop PSU and feeds a fairly large 12V sealed lead-acid battery.

    We are using the following MOSFETs:

    M1, M2, M3: NTMFS5C670NL (60 V, 6.1mΩ, 71A, VGS(th) max. 2V)

    M4: IPD50P04P4L-11 (-40V, 10.6mΩ, -50 A, VGS(th) max. -2.2V)

    Some measured voltages as near to or on the LTC4015 as possible:

    VIN: 18.35V

    IntVCC: 4.05V

    InFET: 20.06V

    OutFET 18.32V

    BG: 0,02 mV

    TG: 12.41V

    2P5Vcc: 2.49V

    Sys: 18.33V

    CSP: 12.54V

    CSPm5: 7.66V

    CLP: 18.33V

    3V3: 3.31V

    UVclb: 600.9mV

    CCRefp: 12.54V

    CCRefm: 12.17V

    Batsens: 12.54V

    NTCbias: 147mV

    VC: 0.53mV

    It seems when I connect a busted lead acid battery that the charger tries to pull OutFET as I can hear clicking in the inductor, but when a good battery is connected as in the case above, it does not appear to try charging at all.

    Some SMBUS data:

    I (708138) batt: LTC4015_NTC_PAUSE_BF: 0
    I (708158) batt: LTC4015_TIMER_TERM_BF: 0
    I (708178) batt: LTC4015_CHARGER_ENABLED_BF: 0
    I (708198) batt: LTC4015_MPPT_EN_PIN_BF: 1
    I (708218) batt: LTC4015_CHARGER_SUSPENDED_BF: 1
    I (708238) batt: LTC4015_CHARGER_STATE_ALERTS: 0
    I (708258) batt: LTC4015_CHARGER_STATE: 256 (100000000)
    I (708278) batt: LTC4015_LIMIT_ALERTS: 0
    I (708298) batt: LTC4015_CHARGE_STATUS_ALERTS: 0
    I (708318) batt: LTC4015_SYSTEM_STATUS: 2759 (101011000111)
    I (708338) batt: LTC4015_EQUALIZE_REQ_BF: 0
    I (708358) batt: LTC4015_DRVCC_GOOD_BF: 1
    I (708378) batt: LTC4015_CELL_COUNT_ERROR_BF: 0
    I (708398) batt: LTC4015_OK_TO_CHARGE_BF: 1
    I (708418) batt: LTC4015_NO_RT_BF: 0
    I (708438) batt: LTC4015_THERMAL_SHUTDOWN_BF: 0
    I (708458) batt: LTC4015_VIN_OVLO_BF: 0
    I (708478) batt: LTC4015_VIN_GT_VBAT_BF: 1
    I (708498) batt: LTC4015_ABSORB_TIMER: 0
    I (708518) batt: LTC4015_EQUALIZE_TIMER: 0
    I (708538) batt: LTC4015_C_OVER_X_TERM_BF: 0
    I (708558) batt: LTC4015_VIN_UVCL_ACTIVE_BF: 0
    I (708578) batt: LTC4015_IIN_LIMIT_ACTIVE_BF: 0
    I (708598) batt: LTC4015_CONSTANT_CURRENT_BF: 0
    I (708618) batt: LTC4015_CONSTANT_VOLTAGE_BF: 0
    I (708638) batt: LTC4015_CHEM_BF: 8
    I (708658) batt: LTC4015_CELL_COUNT_PINS_BF: 6
    I (708678) batt: LTC4015_MEAS_SYS_VALID: 1
    I (708698) batt: LTC4015_IIN_LIMIT_SETTING: 10.67 A
    I (708718) batt: LTC4015_ICHARGE_TARGET_BF: 10.67 A
    I (708738) batt: LTC4015_VCHARGE_SETTING: 2.20 V/cell (13.20 V/tot)
    I (708758) batt: LTC4015_IBAT: 0.00 μA (0.00 mA)
    I (708778) batt: LTC4015_VBAT: 2085936.22 μV (2085.94 mV)
    I (708798) batt: LTC4015_VBAT_FILT: 11.12 mV
    I (708818) batt: LTC4015_VSYS: 18.2862 V
    I (708838) batt: LTC4015_VIN: 18.3389 V
    I (708858) batt: LTC4015_IIN: 0.0000 mA
    I (708878) batt: LTC4015_DIE_TEMP: 34.76 °C
    I (708898) batt: LTC4015_NTC_RATIO: 10037.61 ohm
    I (708918) batt: LTC4015_BSR: 0.00 ohm
    I (708938) batt: LTC4015_QCOUNT: 32768 C

    IBAT and IIN do show values most of the time, but there is a bit of intermittency, this is just cut from a random reporting cycle.

    •  Analog Employees 
    on Jun 26, 2020 7:08 PM 4 months ago in reply to Preben

    Hi all, I sent you both friend requests. You can privately message me your KiCad project or gerbers so I can look at the layout.

    Let's keep the discussion public to help others, though.

    Regards,

    Zack

  • on Jul 6, 2020 1:21 PM 4 months ago in reply to Zack

    We're working with the theory at the moment that our issues are caused by a too long high speed switching path, with too poor connection to ground as the symptoms seem to fit a previous poster. Primarily for the switching path, our C1 was quite far from the other components.

    We've tried to make a new outlay rectifying these two issues, so if you agree this is the likely culprit I will order up a test batch of these and give them a try.

    Best regards,

    Preben

  • on Jul 11, 2020 12:06 PM 4 months ago in reply to Preben

    If you have time to take a quick look at the latest revision we sent we would very much appreciate it as we are behind in our schedule, and have to get a new testbatch out on monday. It would be great to have some feedback so as to not risk another setback. Best regards Preben

    •  Analog Employees 
    on Jul 13, 2020 10:47 PM 4 months ago in reply to Preben

    Hi Preben, I have given you some feedback.